Measuring the Residual Phase Noise of Photodiodes Using Two-Tone Correlation Method

In this letter, we propose a novel approach to measure the residual phase noise (RPN) of a photodiode (PD) using two-tone correlation method. Based on this method, the phase noises of the microwave sources and noise contributions from other components in different paths are suppressed mostly because they are all uncorrelated while the RPN of the PD is preserved. We have measured the RPNs of the PD with different incident optical power to find out the relationship between the RPN and RF tone compression due to the nonlinearity of the PD. The RPN varies significantly along with the increase of RF compression. The RPN jumps up by 15 dB when the RF compression is 1.9 dB compared with 0.2 dB.